The present invention relates to an electromagnetic valve for a flow control which is used as a constant speed air release valve for a blood pressure valve or the like, and particularly to a flow control valve which has a simple structure and can gradually increase an air volume displacement.
Various kinds of blood pressure gauges are proposed, however, there is a blood pressure gauge structured such as to feed an air to a cuff wound around an arm of a person under measurement of blood pressure by a pump, increase a pressure within the cuff to a predetermined value, thereafter gradually reduce the pressure and measure the blood pressure in a pressure reducing step. The structure is made such as to reduce the pressure within the cuff after measuring the blood pressure so as to release a feeling of pressure applied to the arm of the person under measurement of blood pressure, and take out the cuff from the arm.
In the flow control valve of the blood pressure gauge mentioned above, it is important to gradually reduce the pressure within the pressurized cuff, and accordingly it is necessary to gradually increase a size of a pressure outflow port communicated with the cuff. A representative flow control valve as mentioned above is described in Japanese Unexamined Patent Publication No. 6-47007. The flow control valve is constituted by an air outflow port communicated with the cuff, a packing closing the outflow port and mounted to a front end of a movable shaft, and a solenoid driving the movable shaft in an axial direction.
The flow control valve described in the publication mentioned above is structured such that the air outflow port and respective end surfaces of the packing are formed in a flat surface having no parallel relation to each other, and the air outflow port is opened not all at once but step by step by gradually moving the packing apart from the air outflow port. The structure is made such as to cut an electric current of a solenoid so as to press down the movable shaft by a spring after the measurement of the blood pressure is finished by reducing the pressure within the cuff to a predetermined value, thereby quickly reducing the pressure within the cuff to an atmospheric pressure.
However, the flow control valve described in the publication mentioned above is structured such that any one of an end surface of the air outflow port or an end surface of the packing is slightly inclined with respect to a moving direction of a sliding shaft, however, an outflow amount of air is affected by an attitude of the packing. Accordingly, it is necessary to precisely adjust an angle of incline of the air outflow port and the respective end surfaces of the packing, and it is necessary to adjust so that the attitude of the movable shaft smoothly moves without changing.
Accordingly, an object of the present invention is to provide a flow amount control valve structured such as to gradually increase an air outflow amount while having a simple structure.
Further, an object of the present invention is to provide a flow control valve which can intend to achieve a cost cutting by reducing a number of parts.
Further, an object of the present invention is to provide a flow control valve which can control a little amount discharge.
A flow control valve in accordance with the present invention is constituted by an outflow port for flowing out a pressurized fluid to an external portion, a valve body having a pressure contact portion for optionally opening and closing the outflow port, and a valve operating body for moving the pressure contact portion of the valve body, characterized in that a flat surface of the pressure contact portion of the valve body closing the outflow port is formed so as to be inclined by a discharge air from the outflow port.
Further, the valve body is provided with supporting plates in a lower end portion of the pressure contact portion to which a core is fitted and inserted from a bottom opening of a substantially cylindrical packing, at an angle of 180 degrees therefrom. The substantially cylindrical packing and the supporting plates are integrally formed by an elastic member such as a rubber, a plastic or the like. It is preferable that a width of the supporting plate is set to be substantially the same as an outer diameter of the pressure contact portion.
At a time of discharging the air from the outflow port, in order to incline the flat surface of the pressure contact portion in the valve body by the discharge air from the outflow port, the structure may be formed so as to shift a center of the outflow port from a center of the pressure contact portion in the valve body. In order to shift the center of the outflow port from the center of the pressure contact in the valve body, for example, the outflow port may be formed so as to be shifted from an axis of a connection pipe communicated with the cuff, or one of the supporting plates in the valve body may be formed shorter than another so as to be shifted from the center of the pressure contact portion.
Further, at a time of discharging the air from the outflow port, in order to incline the flat surface of the pressure contact portion in the valve body by the discharge air from the outflow port, the structure may be formed so as to make a thickness of one of the supporting plates in the valve body smaller than that of another, or fit and insert the core at a position shifted from the center of the cylindrical packing, thereby making a spring action of one of the supporting plates smaller than that of another.
In the case of forming the outflow port so as to shift from the axis of the connection pipe communicated with the cuff, the discharge air is brought into contact with the position shifted from the center of the pressure contact portion, so that the flat surface of the pressure contact portion is inclined. Further, if one of the supporting plates of the valve body is formed shorter than another, the outflow port is shifted from the center of the pressure contact portion, and a difference is generated in the spring action of the supporting plates, so that the flat surface of the pressure contact portion is inclined by the discharge air.
Further, in the case of forming the thickness of one of the supporting plates in the valve body smaller than the thickness of another, or in the case of fitting and inserting the core so as to shift from the center of the cylindrical packing in the valve body, the spring action of one supporting plate becomes weaker than the spring action of another supporting plate, so that the flat surface of the pressure contact portion in the valve body tends to be inclined by the discharge air from the outflow port.
Further, grooves or slits may be formed in the supporting plates of the valve body. By forming the grooves or the slits, the spring action of the supporting plates becomes small, and it is possible to restrict a back action even in the case that a pressure of the discharge air from the outflow port becomes small. Accordingly, it is possible to maintain the incline of the flat surface of the pressure contact portion in the valve body for a long time, and it is possible to further precisely control the discharge air.
The grooves or the slits formed in the supporting plates in the valve body may be symmetrically or asymmetrically formed in both sides of the pressure contact portion. Further, a shape of the groove or the slit is not particularly limited, may be formed in a circular arc shape, may be formed in a right angle direction with respect to side surfaces of the supporting plates, or may be formed in an oblique direction with respect to the side surfaces of the supporting plates.